In recent years, hybrid vehicles, fuel cell vehicles, downsizing vehicles with supercharger or the like become widespread, and there is an increasing demand for cooling multiple medium as social needs. To effectively cool multiple medium in a small space, a so-called complex heat exchanger (also referred to as multifunction radiator) configured to work on multiple heat exchanging systems is proposed (see Patent Document 1, for example). The heat exchanger disclosed in Patent Document 1 includes tubes for a first heat exchanging system and tubes for a second heat exchanging system, and inside spaces of header tanks are partitioned by screen so as to correspond to each system.